This volume contains 70 photogravure plates of Keeler’s remarkable series of photographs of spiral nebulae, which revealed their abundance amongst nebulous objects in the sky, and led to the realization that they were exterior galaxies.

The work is a triumph of astrophysical and observational skills, astrophotography, and of photogravure as a medium of astronomical illustration. The work documents James Edward Keeler’s investigations with the Crossley reflector at the Lick Observatory. He took up his post there in 1886, while the observatory was under construction; in 1898 he became director, succeeding Edward S. Holden. Keeler was able to put into use the thirty-six inch Crossley reflecting telescope, which had defied earlier astronomers (it was difficult to operate because of an unusual mounting, designed, furthermore, for its original location in England). With the Crossley, Keeler took a series of photographs that revealed how greatly spiral nebulae – later identified as exterior galaxies – outnumbered all the other hazy objects detectable in the sky. Keeler died in 1900, while awaiting a slitless spectrograph he had designed for use with the Crossley telescope. His work on the spiral nebulae was completed by Charles Dillon Perrine (1867-1951), who oversaw the publication of this volume. Keeler’s successor William Wallace Campbell was the photographer that attempted to assist Einstein in proving his theory of relativity by attempting the photographing of light bending around a total eclipse of the sun at the beginning of WW1. The sky was cloudy preventing the photograph which actually saved Einstein form embarrassment of being wrong. [1]